Strip-coating apparatus

ABSTRACT

Strip-coating apparatus including a tank divided into a pair of end chambers and an intermediate chamber by a pair of vertical plates projecting into the tank from an upper sealing plate thus to eliminate disturbance of the liquid surface in the intermediate chamber by strip material entering and leaving the two end chambers.

United States Patent [56] References Cited UNITED STATES PATENTS 786,727 4/1905 Cazin 118/50 X 1,924,142 8/1933 Willauer .1 117/115 1,930,601 10/1933 Townsend ..1 17/1 14 (B) UX 2,125,364 8/1938 Waldron 1 118/50 2,197,622 4/1940 Sendzimin.. 118/67 X 2,203,241 6/1940 Waldron 1 18/50 2,226,360 12/1951 Spickelmier et al.. 118/12 X 2,542,064 2/1951 Tilden 118/419 X 3,268,422 8/1966 Smith et a1 117/1 14 (C) X 3,291,639 12/1966 Flowers et a1.' 118/67 X Primqry Examiner-Morris Kaplan Attorney-Oberlin, Maky,Donne1ly & Renner ABSTRACT: Strip-coating apparatus including a tank divided into a pair of end chambers and an intermediate chamber by a PATENTED JUNZSIQII 3,539,330

IN VE N71 )H ALEXANDER V. ALEXEFF STRIP-COATING APPARATUS BACKGROUND OF THE INVENTION The present invention relates generally as indicated to strip coating apparatus and more particularly to apparatus for ap plying a coating such as natural rubber in a highly volatile solvent to web or strand material by passing the same through the tank while keeping the amount of vaporization of the solution to a minimum.

Certain web and strand materials such as synthetic rubber used in the manufacture of pneumatic tires for airplanes and the like are generally coated with a solution of natural rubber in a high octane gas solvent to obtain the high degree of adhe sion required between the tire plies during the manufacturing process. Because of the highly volatile and explosive nature of the solution, it is extremely important that spilling and vaporization be kept to a minimum and that the vapor which does form be removed so that it is kept below an explosive level.

A substantially closed tank will prevent the solution from spilling, but the surface turbulence created by the web material entering and leaving the solution promotes vaporization to such an extent that large quantities of air must be circulated through the tank to prevent the vapor from accumulating above a dangerous level therein. A reduction in the amount of vaporization of the solution can be achieved by placing the tank in an enclosure and cooling the vapor to cause condensation while at the same time reducing the exposed surface area by the condensing tank, but a large volume of air is still required to ventilate the enclosure. In actual practice, approximately 10,000 cubic feet per minute of air at 70 F. per gallon of solvent is used to keep the enclosure safe from explosions. Of this air, about one third is required to remove the vapor from the material when in the drying ovens away from the tank; the other two thirds is for removing the vapor from the enclosure itself.

SUMMARY OF THE INVENTION With the foregoing in mind, it is a principal object of this invention to provide an improved coating apparatus which reduces the amount of vaporization of the volatile solvent and thus requires considerably less air for ventilation.

Another object is to provide such an apparatus in which the exposed surface of the solution in the region between where the material enters and leaves the solution is isolated from the rest of the tank surface.

A further object is to provide such an apparatus in which the tank is completely removable from the remainder of the apparatus to facilitate cleaning and replacement.

Another object is to provide such an apparatus in which no enclosure is required around the same, at a substantial savings in cost.

Yet another object is to provide such an apparatus which may be completely ventilated through the drying oven as sociated therewith.

These and other objects of the present invention may be achieved by dividing the tank containing the solution into plural chambers by a plurality of vertical plates projecting into the tank from an upper sealing plate. The end chambers are for the incoming and outgoing strip material, and are quite small to reduce to a minimum the surface area that is disturbed by the strip material entering and leaving the solution. The tank is desirably removably clamped to the upper sealing plate to facilitate removal and replacement.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principles of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWING In the annexed drawing:

FIG. 1 is a longitudinal section through a preferred form of strip-coating apparatus constructed in accordance with this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The coating apparatus 1 illustrated herein by way of example generally comprises a tank 2 having an open top 3 which is adapted to be closed by engagement of the upper edge of the tank with a top sealing plate 5 desirably fixedly located adjacent a drying oven 6 in a strip-processing line. The tank 2 may be pressed tightly up against the top sealing plate 5 as by actuation of two or more hydraulic cylinders 10 engageable with the base 1] thus making the tank completely portable to facilitate ready removal and replacement of the tank 2 as required, but of course a permanent connection may be pro vided between the tank 2 and sealing plate 5 ifdesired. Casters 12 or the like may be mounted on the base 11 for guiding the tank 2 along parallel tracks 13 upon retraction of the hydraulic cylinders 10. To preclude spilling of the solution 15 from within the tank 2 and escape of vapors between the top sealing plate 5 and upper edge of the tank to the atmosphere, a labyrinth-type seal 16 is provided therebetween desirably formed as by engagement of a bar 17 with the top sealing plate 5, such bar l7 being bolted or otherwise secured to the tank angle 18 and extending around the entire periphery of the tank 2 for receipt between a pair of bars 19 of less height welded to the top sealing plate 5.

Projecting downwardly from the top sealing plate 5 is a pair of laterally spaced, vertically extending plates or partitions 20 and 21 which are adapted to be received in the tank 2 between the sidewalls 22 thereof thus to divide the interior of the tank 2 into a pair of relatively narrow end chambers or zones 23 and 24 separated by a larger intermediate chamber or zone 25. The end chambers 23 and 24 are the entrance and exit zones for the strip material S which may be of a synthetic rubber fabric as aforesaid. Before entering the end chamber 23, the strip material S is directed through a labyrinth-type seal 27 having a plurality of narrowly spaced-apart flexible plastic strips 28 covering the entrance port 29. From there the strip S is guided around a plurality of rolls 30 and 31 suitably journaled in the tank 2 below the partitions 20 and 21 for directing the strip material downwardly through the entrance chamber 23 and below the intermediate chamber 25 for exit upwardly through the exit chamber 24 and out the exit port 32 which opens into a chamber 33 leading to the drying oven 6. Within the chamber 33, there are provided a pair of scraper bars 34 and air wipers 35 which remove most of the liquid from the surface of the material as it passes therebetween, and cause the liquid to fall back into the tank 2 through the exit port 32 guided by the inclined surfaces 36.

The partitions 20 and 21 extend downwardly into the tank 2 sufficiently below the, normal liquidl level therein that the liquid surface in the region of the intermediate zone 25 is not disturbed by the strip material S entering and leaving the liquid in the end zones 23 and 24 thus to reduce substantially the amount of vaporization of the solution in the intermediate zone. Moreover, because the end zones 23 and 24 where the liquid disturbance is the greatest are relatively small, the high vapor areas are also quite small. Despite such vapor, however, the tank 2 need not be ventilated since it is completely sealed. Only the oven 6 need be ventilated, whereby only about one third of the air is required to remove the vapor than if the tank also had to be ventilated. And of course there is a reduced amount of air pollution because less solvent vapor is being dumped into the atmosphere.

Sufficient venting of the exit zone 24 occurs through the exit port 32 which is connected to the drying oven 6 through the chamber 33 as aforesaid. It may also be desirable to provide a vent 40 for the intermediate zone 25 which may be connected to the suction side of the drying oven 6 to prevent any possibility of positive pressure buildup in the tank. Similarly, the entry zone 23 may be vented to the drying oven 6 as by providing a vent opening 41 in the partition 20 above the liquid level, or by connecting the zone 23 to the zone 24 along one or both sides of the tank. By maintaining the drying oven 6 under negative pressure, leakage of any of the volatilized gas to the atmosphere between the top sealing plate and tank 2 is precluded even should the seals 16 not be absolutely airtight.

As a safety precaution, liquid should only be pumped into the tank 2 through the pipe connection 42 when the hydraulic cylinders are actuated and the tank 2 in in firm sealing engagement with the top sealing plate 5. A limit switch 43 or other such control device may be provided on the top sealing plate 5 to preclude actuation of the'liquid pump 44 except when the tank is in proper sealing contact thereagainst. Moreover, special care should be taken to make sure that the liquid does not overflow when pumped into the tank, as by providing an overflow switch 45 within the tank to stop the pump when the desired liquid level is reached. Carbon dioxide or other inert gas may be continuously supplied to the tank to cover the solvent surface during use to further reduce volatilization, or automatically released into the tank only in the event of a fire.

Additional switching devices 46 and 47 of suitable type may also be provided within the tank which detect the presence of liquid and volatilized vapor within the tank to prevent lowering by actuation of the cylinders 10 until the tank is empty and the volatilized vapor within the tank is at a safe level. Such switching devices 46 and 47 may also be used to keep the oven fans running until the tank is completely empty and ventilated.

From-the foregoing, it can now be seen that the coating apparatus of the present invention prevents the dip solution and volatized solvents from being spilled on the floor or escaping into the surrounding atmosphere, whereby no enclosure is required around the tank and the tank itself need not be ventilated. Ventilation is only required of the oven, whereby the amount of air needed may be reduced approximately twothirds of the amount used on previous designs and accordingly smaller size fans may be used. The amount of surface area of the liquid that is disturbed by the incoming and outgoing length of material is kept to a minimum by partitioning off the incoming and outgoing zones.

1, therefore, particularly point out and distinctly claim as my invention:

1. Apparatus for coating a traveling strip with a liquid coating comprising a tank, a sealing plate enclosing the top of said tank, vertical partitions extending downwardly from said sealing plate into said tank below the normal level of liquid coating in said tank to provide an entry zone and an exit zone for the strip material separated by an intermediate zone, and means for guiding the strip downwardly into the entry zone and below the intermediate zone for exit upwardly through the exit zone, said vertical partitions substantially eliminating disturbance of the liquid surface in said intermediate zone by the strip entering and leaving the entry and exit zones, said sealing plate having an entrance port communicating with said entry zone and an exit port communicating with said exit zone, means for providing a fluid seal between the strip material and entrance port, a chamber communicating said exit port with a drying oven for the strip leaving the tank, said exit zone having open communication with said oven through said exit port and chamber, means for ventilating said oven thus to ventilate said exit zone through said chamber and exit port, and a vent opening in the partition between said entry zone and intermediate zone above the liquid level in said tank for venting said entry zone to said oven through said intermediate zone and vent.

2. The apparatus of claim 1 wherein said drying oven is maintained under negative pressure, whereby leakage of vapor within said tank to the atmosphere between said sealing plate and tank is precluded even though the seal therebetween in? not be airtight.

. Apparatus for coating a traveling strip with a highly volatile liquid coating comprising a tank, a sealing plate enclosing the top of said tank, a pair of vertical partitions extending downwardly from said sealing plate into said tank below the normal level of liquid coating in said tank to provide an entry zone and an exit zone for the strip material separated by an intermediate zone, said partitions dividing said tank into relatively small end zones at opposite ends of the tank which are said entry and exit zones and a relatively large intermediate zone between said end zones, and means for guiding the strip downwardly into the entry zone and below the intermediate zone for exit upwardly through the exit zone, said vertical partitions substantially eliminating disturbance of the liquid surface in said intermediate zone by the strip entering and leaving the entry and exit zones, said sealing plate having an entrance port communicating with said entry zone and an exit port communicating with said exit zone, means for providing a fluid seal between the strip material and entrance port, a chamber communicating said exit port with a drying oven for the strip leaving the tank, said exit zone having open communication with said oven through said exit port and chamber, and means for ventilating said oven thus to ventilate said exit zone through said chamber and exit port, and means in said chamber for removing excess liquid from the strip as it passes through said chamber to said oven.

4. Apparatus for coating a traveling strip with downwardly into highly volatile liquid coating comprising a tank, a sealing plate enclosing the top of said tank, a pair of vertical partitions extending downwardly from said sealing plate into said tank below the normal level of liquid coating in said tank to provide an entry zone and an exit zone for the strip material separated by an intermediate zone, said partitions dividing said tank into relatively small end zones at opposite ends of the tank which are said entry and exit zones and a relatively large intermediate zone between said end zones, and means for guiding the strip downwardly into the entry zone and below the intermediate zone for exit upwardly through the exit zone, said vertical partitions substantially eliminating disturbance of the liquid surface in said intermediate zone by the strip entering and leaving the entry and exit zones, said sealing plate have an entrance port communicating with said entry zone and an exit port communicating with said exit zone, means for providing a fluid seal between the strip material and entrance port, a chamber communicating said exit port with a drying oven for the strip leaving the tank, said exit zone having open communication with said oven through said exit port and chamber, and means for ventilating said oven thus to ventilate said exit zone through said chamber and exit port, and a vent for said intermediate zone communicating with said drying oven.

5. The apparatus of claim 4 wherein said sealing plate is fixedly located in a stripprocessing line and said tank is movable into and out of engagement with said sealing plate, and means are provided for releasably pressing said tank against said sealing plate thus to facilitate ready removal and replacement of said tank.

6. The apparatus of claim 4 wherein said tank has a bar secured thereto around the upper periphery thereof, and said sealing plate has a pair of laterally spaced-apart bars secured thereto of less height than said bar on said tank for receipt of said bar on said tank therebetween to provide a labyrinth-type seal when said tank is pressed against said sealing plate as aforesaid.

7. The apparatus of claim 4 further comprising pump means which when actuated fills said tank, and switch means for preventing actuation of said pump means except when said tank is pressed against said sealing plate as aforesaid.

8. The apparatus of claim 4 further comprising switch means within said tank for detecting the presence of liquid and volatilized vapor preventing actuation of said clamp means to release said tank from said sealing plate until said tank is empty and ventilated. 

2. The apparatus of claim 1 wherein said drying oven is maintained under negative pressure, whereby leakage of vapor within said tank to the atmosphere between said sealing plate and tank is precluded even though the seal therebetween may not be airtight.
 3. Apparatus for coating a traveling strip with a highly volatile liquid coating comprising a tank, a sealing plate enclosing the top of said tank, a pair of vertical partitions extending downwardly from said sealing plate into said tank below the normal level of liquid coating in said tank to provide an entry zone and an exit zone for the strip material separated by an intermediate zone, said partitions dividing said tank into relatively small end zones at opposite ends of the tank which are said entry and exit zones and a relatively large intermediate zone between said end zones, and means for guiding the strip downwardly into the entry zone and below the intermediate zone for exit upwardly through the exit zone, said vertical partitions substantially eliminating disturbance of the liquid surface in said intermediate zone by the strip entering and leaving the entry and exit zones, said sealing plate having an entrance port communicating with said entry zone and an exit port communicating with said exit zone, means for providing a fluid seal between the strip material and entrance port, a chamber communicating said exit port with a drying oven for the strip leaving the tank, said exit zone having open communication with said oven through said exit port and chamber, and means for ventilating said oven thus to ventilate said exit zone through said chamber and exit port, and means in said chamber for removing excess liquid from the strip as it passes through said chamber to said oven.
 4. Apparatus for coating a traveling strip with downwardly into highly volatile liquid coating comprising a tank, a sealing plate enclosing the top of said tank, a pair of vertical partitions extending downwardly from said sealing plate into said tank below the normal level of liquid coating in said tank to provide an entry zone and an exit zone for the strip material separated by an intermediate zone, said partitions dividing said tank into relatively small end zones at opposite ends of the tank which are said entry and exit zones and a relatively large intermediate zone between said end zones, and means for guiding the strip downwardly into the entry zone and below the intermediate zone for exit upwardly through the exit zone, said vertical partitions substantially eliminating disturbance of the liquid surface in said intermediate zone by the strip entering and leaving the entry and exit zones, said sealing plate have an entrance port communicating with said entry zone and an exit port communicating with said exit zone, means for providing a fluid seal between the strip material and entrance port, a chamber communicating said exit port with a drying oven for the strip leaving the tank, said exit zone having open communication with said oven through said exit port and chamber, and means for ventilating said oven thus to ventilate said exit zone through said chamber and exit port, and a vent for said intermediate zone communicating with said drying oven.
 5. The apparatus of claim 4 wherein said sealing plate is fixedly located in a strip-processing line and said tank is movable into and out of engagement with said sealing plate, and means are provided for releasably pressing said tank against said sealing plate thus to facilitate ready removal and replacement of said tank.
 6. The apparatus of claim 4 wherein said tank has a bar secured thereto around the upper periphery thereof, and said sealing plate has a pair of laterally spaced-apart bars secured thereto of less height than said bar on said tank for receipt of said bar on said tank therebetween to provide a labyrinth-type seal when said tank is pressed against said sealing plate as aforesaid.
 7. The apparatus of claim 4 further comprising pump means which when actuated fills said tank, and switch means for preventing actuation of said pump means except when said tank is pressed against said sealing plate as aforesaid.
 8. The apparatus of claim 4 further comprising switch means within said tank for detecting the presence of liquid and volatilized vapor preventing actuation of said clamp means to release said tank from said sealing plate until said tank is empty and ventilated. 